1. Field of the Invention
This invention relates to an aircraft wing which exhibits reduced airframe-generated noise, and to a method of reducing noise generated by an aircraft wing. More particularly, the aircraft wing of this invention has a leading edge slat which cooperates with the wing main element. One or more sound-absorbing or acoustically treated structures are employed on the forward edge of the main element and the trailing edge of the slat, or in the cavity formed between the slat and the main element, or both, to reduce airframe-generated noise.
2. Background Information
The desirability of reducing the noise generated by an aircraft is well-known to those skilled in the art. As discussed, for example, in U.S. Pat. No. 5,749,546, both the airplane""s airframe and engines produce varying amounts of objectionable audible noises during departure and approach conditions. More particularly, airframe noise is generated by a fluid (such as air) flowing over the airplane""s fuselage, landing gear, wing, and wing leading edge, and high-lift devices such as slats and trailing edge flap systems.
U.S. Pat. No. 5,749,546 is directed to reducing the noise generated by an aircraft airframe by providing a rounded flap edge cap to reduce any noise-generating secondary vortices that may be produced by the flap edge when it is exposed to a fluid such as air while the wing is moving.
U.S. Pat. No. 5,738,298 is directed to an aircraft wing having an apparatus for reducing lift-generated noise caused by the high lift system of the aircraft wing, i.e. the slat system located on the forward edge of the aircraft wing. The apparatus employed is a plurality of tip fences secured to the trailing and leading assemblies of the high-lift system, as close as possible to the discontinuities where the noise-generating vortices are most likely to form.
However, there are likely to be instances in which use of a tip fence such as disclosed in U.S. Pat. No. 5,738,298 is less preferable than a method of reducing airframe-generated noise produced by the high-lift system in which the assembly used therein more closely conforms to the airfoil design and shape. Moreover, it is known that the downward directed noise component generated by the cavity located between the slat trailing edge and wing leading edge is a major contributor to noise heard by ground-based observers.
Accordingly, it is one object of this invention to provide an aircraft wing which employs an assembly which closely aligns with the contours of the airfoil shape and design and which reduces noise generated by the wing, and particularly noise generated by the cavity located between the slat trailing edge and wing leading edge. It is one feature of this invention that the assembly may be one or more sound-absorbing or acoustically treated structures positioned on the forward edge of the wing main element or the trailing edge of the slat, or both. It is another feature of this invention that the assembly may be one or more sound-absorbing or acoustically treated structures positioned in the cavity formed between the slat and the main element. It is another feature of this invention that the assembly may include combinations of the above-described structures positioned: (i) on the forward edge of the wing main element; (ii) on the trailing edge of the slat; and (iii) in the cavity formed between the main element and the slat.
It is another object of this invention to provide a method of reducing noise generated by an aircraft wing using the above-described assembly. Other objects, features and advantages of this invention will be apparent from the detailed description set forth below.
An aircraft wing useful for reducing wing-generated noise comprises:
(a) a main element having a leading edge and a trailing edge;
(b) at least one slat having a leading edge and a trailing edge, wherein the slat acts cooperatively with the main element to provide lift to the aircraft, and the main element leading edge and slat trailing edge define a cavity therebetween; and
(c) at least one sound-absorbing structure located on at least a portion of the main element leading edge, at least a portion of the slat trailing edge, in the cavity, or combinations thereof.
If located on the main element leading edge or slat trailing edge, the sound-absorbing structure may be a honeycomb load-bearing structure such as a honeycomb load-bearing structure having a perforated skin or a machine grid structure having an outer skin which is bonded or perforated. If located in the cavity, the sound-absorbing structure may be a flow blocker. The sound-absorbing structure is typically covered during the normal cruise portion of the aircraft""s flight, and thus does not adversely impact aerodynamic performance.
A method of reducing such wing-generated noise comprises providing the above-described wing for use in an aircraft in flight.